I don't think so. He'll definitely get to four sometime but five is 50-50. It's a pretty tough task to win four majors at the Australian Open, let alone five. Agassi's baseline game was suited to the surface (similar to Djokovic's now) and JesusFed only won four each. I believe this surface has a higher chance of a winner coming out of nowhere (judging by past finalists Murray, Tsonga, Gonzales, Baghdatis) and of Novak being in danger of defeat, as evidenced by his SF and F matches. I also think he'll do better at the US Open for some reason – maybe because he has Fed's number there and the faster surface will suit him better as well as hindering Nadal more.
I like Nole's chances at the Australian better than US Open. I think AO is Nole's best slam because his baseline game is so rock solid. He's the only guy on tour who can get into 20 shot rally's with Nadal and win more than he loses. Novak has a good serve, but it isn't amazing so I think he will have a harder time winning multiple US Opens.
Having said that, I like Nole's chances at the US Open this year. He's the best hard court player in the world right now and I'm not sure Del Potro is back to his old self just yet. Once Del Pony gets there though, he will become a major threat at the US Open. IMO anyway.